Titanotheres, also known as
Brontotheriums, are the largest animals found in the White River formation. These
mammals evolved rapidly from their Eocene origins, dramatically increasing in size until
they reached nearly the size of today's elephant. They bore a superficial
resemblance to today's rhinoceros, but were actually more closely related to horses.
The horns at the front of the Titanothere's skull required strengthening of the skull,
which is achieved by the upwards curve of the skull as in the Rhinoceros.
Titanotheres became extinct during the Oligocene at a time when the forests were turning
to grasslands.

Titanotheres are Perissodactyls, odd toed ungulates.

Brontops

The different Titanothere genera of the Chadron formation are distinguished by the
shape and size of their horns as well as the arch of their skull. Animals with heavy
horns tend to have a arched skull for strength. It is thought that the females had
smaller horns.

Skull is 33" long; horns and scattered other places have reconstruction.

One zygomatic arch is missing.

Lower right jaw section is 18" long; contains three teeth.

Top view of right lower jaw, showing three teeth. The tooth on the right is
the last tooth at back of jaw.

Last molar from right upper jaw. The upper molars are twice as wide as the
lower molars.